1. Technical Field of the Invention
The present invention relates to a restarting method when a robot suddenly stops during movement due to an emergency stop.
2. Description of the Prior Art
A robot stores a plurality of positions as teaching points beforehand. When a start button is pressed, the robot moves operation tools such as a hand or a welding gun attached to the wrist of the robot sequentially along teaching routes passing the teaching points according to the teaching program. The robot carries out interpolation calculations on the basis of the position of each teaching point and moves.
When an emergency stop instruction signal such as emergency stop is input during movement of the robot, a brake is applied to a motor for driving each axis of the robot and the excitation of the motor is turned off. The interpolation process is also stopped and a mechanical unit of the robot is decelerated and stopped. When an operation speed of the robot is fast, the robot cannot immediately stop due to an effect of the moment of inertia and others, and the robot stop position is diverted from the teaching route. For example, when the robot suddenly stops at an operation speed of 2000 mm/s, the movement distance to the stop position after the stop instruction signal is input, is about 100 mm, and therefore the stop position is diverted from the teaching route.
Generally, the robot teaching route is taught so as to prevent the operation tools and arm of the robot from interferring with other devices. Therefore, as described before, when the stop position is shifted from the teaching route when the robot stops suddenly and the robots moves to the next teaching point from this shifted position, there is a possibility that the robot interferes with the other devices.
To solve such a problem, for example, in Japanese Patent Laid-Open 5-100732, xe2x80x9cRobot Numerical Controllerxe2x80x9d, a method that when a robot stops in case of emergency, it returns to a position in which the robot has started to stop at a low speed and then moves to the final point at low speed, is disclosed. Therefore, even when the stop position is diverted from a predetermined route, an operator can prevent interference of the robot with other devices by moving it at a low speed and when there is a possibility of interference of the robot with other devices, he can stop the robot immediately and avoid its interference.
However, a problem arises that when the robot moves to the final point at low speed after restarting, the operation efficiency would drastically reduced.
The present invention was developed in consideration of such a problem and is intended to provide a robot restarting method for preventing interference of a robot with other devices and keeping a high operation efficiency.
The present invention is a robot restarting method in which when a robot moving at a predetermined teaching speed along a teaching route passing a plurality of preset teaching points stops at a stop position during movement and restarts thereafter, comprising a step of restarting the robot and a low speed moving step of moving the robot at a lower speed than the teaching speed until it reaches the next first reaching point of the stop position.
The present invention is the robot restarting method further comprising a speed return step of accelerating the robot and returning the robot speed to the teaching speed.
According to the present invention, the robot moves to the next first teaching point after restarting, so that an operator can confirm sufficiently as to whether the robot interferes with other devices and the operation is safe. When the robot reaches the first teaching point, it moves along the teaching route thereafter. Since the teaching route is a route which is taught so as to prevent interference of the robot, the robot can move at the ordinary teaching speed thereafter. Due to this method, the operation efficiency can be improved compared with the conventional method for moving a robot to the final point at a low speed.
The present invention is the robot restarting method further comprising a medium speed moving step of moving the robot at a medium speed which is lower than the teaching speed and higher than the low speed until the robot reaches the next second teaching point from the first teaching point between the low speed moving step and the speed return step.
According to the present invention, the robot moves to the next first teaching point at the low speed and moves to the next second reaching point at the medium speed. The robot increases its speed in two stages so that the speed reaches the teaching speed like this. Therefore it can be prevented from suddenly increasing its speed up to the teaching speed.
The present invention is the robot restarting method in which the robot can change its speed by a restarting button, and the robot is moved by changing its speed by the restarting button in the low speed moving step.
The present invention is the robot restarting method for moving a robot by changing its speed to a fixed acceleration or a fixed speed by the restarting button in the low speed moving step.
According to the present invention, the robot can move by changing its speed to a fixed acceleration or a fixed speed by pressing the restarting button. Therefore, an operator can optionally switch the moving speed depending on the stop state.
The present invention is the robot restarting method for moving the robot at a fixed acceleration in the low speed moving step.
The present invention is the robot restarting method for moving the robot continuously at the same acceleration as that in the low speed moving step until it reaches the teaching speed after the low speed moving step.
According to the present invention, the moving speed can be increased at the fixed acceleration until it can reach the teaching speed, so that at first the robot can move at the low speed to ensure the safety, gradually increase the speed, and then reach to the teaching speed quickly.
The present invention is the robot restarting method for restarting the robot at the stop position.
According to the present invention, the robot restarts so as to directly move toward the next first teaching point from the stop position, so that it can securely restart quickly.
The present invention is the robot restarting method for returning the robot to the return position of the teaching route once from the stop position and then restarting it from the return position.
According to the present invention, the robot returns to the teaching route once and then performs the restarting operation, so that it can securely prevent interference with other devices.
The present invention is the robot restarting method for setting the low speed moving step so as to have a predetermined time.